SimmsFishFence
Eric V
17 February, 2025
1. Introduction
Simms Creek is a small, 3rd order stream that drains an area of ~1,800 ha into the Salish Sea, near Campbell River’s Willow Point neighborhood. The lower reach of Simms Creek (~3 km of channel, east of Jubilee Road), is contained within a narrow urban green way that is bordered by residential properties. From Jubilee Road to the Inland Highway the stream is protected within Beaver Lodge Lands, upstream of the Inland Highway, >1.5 km of tributary channel is located within private forest lands.
Historic fish observations indicate that Chum, Chinook, Pink and Coho salmon have all been observed in the stream, as well as Coastal Cutthroat Trout (CCT), Rainbow Trout and steelhead. More recent monitoring (i.e., this dataset), suggest that Coho Salmon (CO) and CCT are the primary species within Simms Creek, both of which utilize the stream year round - though a small number of juvenile Chinook Salmon were identified in 2024.
Greenways Land Trust has supported Simms Creek Stewards for +20 years, including operation of a fish fence near the mouth of the stream since 2008. Juvenile and adult fish moving past the fence are tallied each spring and fall, respectively. The objective of this project is to explore the juvenile fence dataset. All work is being done strictly for fun and out of personal curiosity. Any feedback, input, or support is welcome. Also, I have a soft spot for CCT, so be warned that effort and results will be slightly trout biased.
Throughout this analysis, I explore what data collected during spring and fall can tell us about:
What species are utilizing Simms Creek?
Whether the current fence operation program is capturing the complete migration period?
When are key behaviours occurring (e.g., when is peak smolt? when do adults arrive?) and are they occurring at consistent times each year?
How large are fish encountered during smolt and upstream migration periods? What age classes are migrating (I don’t have scale data, but we can make an educated guess).
What is the freshwater survival of Coho Salmon? Note that we cannot estimate marine survival without some information on individual fish (i.e., coded wire tag data to verify that returning adults originated in Simms Creek and when they smolted).
What factors may be driving variability in the number of CCT and CO smolts outmigrating each spring and the number of adult CO returning each fall.
But before we can do that, lets take a look at what has been completed to date. It’s a tremendous amount of work and all volunteers and supporters should be commended!
2. Fence Operation
2.1. Monitoring Effort
The Simms Creek fish fence has operated annually since 2008, with the exception of 2020 and 2021 when operations were paused due to the COVID-19 Pandemic and in the spring of 2023 when federal employees were on strike.
Spring surveys target out migrating juvenile Coho Salmon but also capture an impressive number of CCT and have even captured some Chinook Salmon. Spring fence monitoring has started as early as April 03, however, most surveys (50%) don’t start until April 18. In each monitoring year, the fence has operated continuously (e.g., sampling occurred at least daily) from April 28 to May 30. Surveys have continued as late as June 13, but most (50%) are terminated by June 06.
Fall surveys to count the number returning adult Coho, Chinook, Chum and Pink Salmon and also intercept a small number of CCT. In the fall, surveys have started as early as September 26, however, most surveys (50%) have started on October 08. In each monitoring year, surveys have occurred continuously (e.g., sampling occurred daily) from October 23 to November 16. Surveys have continued as late as December 10 and no surveys have occurred later than December 02.
Monitoring Effort Tables and Figures
Table 1. Sampling Summary
| Period | Min | Max | Mean | SD | Min | Max | Mean | SD | Min | Max | Mean | SD |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Spring | 41 | 68 | 51.0 | 7.3 | 03-Apr | 28-Apr | 16-Apr | 7.0 | 30-May | 13-Jun | 05-Jun | 4.4 |
| Fall | 35 | 64 | 50.9 | 10.3 | 26-Sep | 23-Oct | 09-Oct | 7.1 | 16-Nov | 10-Dec | 29-Nov | 7.5 |
Table 2. Annual Spring and Fall Trap Operation Periods
| Year | # Days Sampled | Start | End | # Days Sampled | Start | End |
|---|---|---|---|---|---|---|
| 2008 | 41 | Apr-21 | May-31 | 40 | Oct-14 | Nov-22 |
| 2009 | 50 | Apr-19 | Jun-07 | 40 | Oct-14 | Nov-22 |
| 2010 | 42 | Apr-19 | May-30 | 35 | Oct-23 | Nov-26 |
| 2011 | 49 | Apr-19 | Jun-06 | 46 | Oct-18 | Dec-02 |
| 2012 | 50 | Apr-16 | Jun-04 | 50 | Oct-14 | Dec-02 |
| 2013 | 49 | Apr-14 | Jun-01 | 62 | Sep-29 | Dec-01 |
| 2014 | 45 | Apr-24 | Jun-07 | 58 | Oct-04 | Nov-30 |
| 2015 | 52 | Apr-10 | May-31 | 62 | Oct-08 | Dec-08 |
| 2016 | 63 | Apr-03 | Jun-04 | 60 | Oct-07 | Dec-05 |
| 2017 | 68 | Apr-05 | Jun-11 | 56 | Oct-11 | Dec-05 |
| 2018 | 52 | Apr-21 | Jun-11 | 58 | Oct-08 | Dec-04 |
| 2019 | 51 | Apr-18 | Jun-07 | 64 | Oct-08 | Dec-10 |
| 2020 | 0 | COVID |
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| 2021 | 0 | COVID |
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| 2022 | 47 | Apr-28 | Jun-13 | 37 | Oct-11 | Nov-16 |
| 2023 | 0 | DFO Strike |
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45 | Sep-26 | Nov-17 |
| 2024 | 55 | Apr-12 | Jun-05 | 0 |
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2.2 Stream Conditions
During each daily trap visit, volunteers record measures of water temperature, pH, Total Suspended Sediment (TSS), dissolved oxygen, and water level (stage). Mean annual measures of each parameter are presented below for the spring and fall monitoring periods (Table 3 and Table 4, Figure 2).
Stream Conditions Figures and Tables
Table 3. Spring Condition Table
| Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2008 | 9.5 | 4.0 | 10.5 | 2.8 | 7.1 | 0.3 | 10.8 | 0.8 | 67.8 | 36.8 | 0.2 | 0.0 |
| 2009 | 11.8 | 3.0 | 10.3 | 2.4 | 7.1 | 0.2 | 10.3 | 0.8 | 136.4 | 26.2 | 0.3 | 0.0 |
| 2010 | 9.5 | 2.2 | 10.0 | 1.6 | 8.2 | 0.3 | 10.5 | 1.8 | 110.2 | 17.4 | 0.2 | 0.1 |
| 2011 | 9.8 | 2.3 | 9.8 | 2.1 | 6.7 | 0.3 | 9.1 | 1.0 | 95.5 | 11.7 | 0.2 | 0.0 |
| 2012 | 11.0 | 2.1 | 10.2 | 1.7 | 7.4 | 0.8 | 9.9 | 1.4 | 99.4 | 17.2 | 0.2 | 0.1 |
| 2013 | 10.3 | 2.9 | 10.1 | 2.0 | 7.9 | 0.3 | 11.5 | 0.9 | 100.6 | 14.9 | 0.2 | 0.1 |
| 2014 | 12.2 | 2.4 | 11.3 | 1.7 | 8.1 | 0.5 | 9.7 | 0.6 | 97.8 | 19.2 | 0.2 | 0.1 |
| 2015 | 10.5 | 3.4 | 11.0 | 2.5 | 8.1 | 0.2 | 9.4 | 0.8 | 106.7 | 22.2 | 0.2 | 0.4 |
| 2016 | 11.4 | 2.8 | 11.7 | 1.8 | 7.1 | 0.4 | 10.2 | 1.5 | 111.3 | 20.1 | 0.1 | 0.0 |
| 2017 | 9.6 | 3.0 | 10.2 | 2.3 | 8.2 | 0.4 | 10.9 | 2.2 | 77.8 | 25.6 | 0.3 | 0.1 |
| 2018 | 10.7 | 2.5 | 8.7 | 1.3 | 8.8 | 1.4 | 14.2 | 1.6 | 153.9 | 21.2 | 0.1 | 0.0 |
| 2019 | 11.2 | 2.7 | 11.9 | 2.3 | 8.0 | 0.2 | 8.6 | 0.7 | 129.0 | 25.7 | 0.1 | 0.1 |
| 2022 | 11.7 | 2.5 | 12.2 | 16.0 | 7.5 | 0.3 |
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83.0 | 17.2 | 0.2 | 0.1 |
| 2023 |
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| 2024 | 12.1 | 2.2 | 10.3 | 2.1 | 7.7 | 0.4 | 10.2 | 0.9 | 129.8 | 30.0 | 0.1 | 0.0 |
Table 4. Fall Condition Table
| Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2008 | 6.3 | 3.0 | 8.8 | 1.3 | 7.3 | 0.4 | 10.5 | 0.4 | 120.2 | 30.9 | 0.4 | 0.1 |
| 2009 | 6.8 | 3.3 | 8.7 | 1.9 | 7.6 | 0.2 | 10.6 | 1.9 | 105.0 | 28.7 | 0.5 | 0.2 |
| 2010 | 4.9 | 4.7 | 7.9 | 2.7 | 7.0 | 0.2 | 9.5 | 0.9 | 110.9 | 31.1 | 0.6 | 0.9 |
| 2011 | 4.9 | 3.0 | 7.0 | 1.8 | 7.3 | 0.6 | 9.7 | 0.5 | 112.7 | 30.1 | 0.3 | 0.3 |
| 2012 | 5.9 | 3.2 | 7.8 | 1.7 | 7.5 | 0.2 | 10.8 | 1.6 | 116.1 | 29.6 | 0.4 | 0.2 |
| 2013 | 6.1 | 3.1 | 8.0 | 2.0 | 7.7 | 0.1 | 10.5 | 0.7 | 119.8 | 30.6 | 0.3 | 0.1 |
| 2014 | 7.3 | 5.0 | 9.6 | 3.2 | 7.9 | 0.2 | 10.0 | 1.2 | 85.3 | 29.8 | 0.3 | 0.1 |
| 2015 | 6.0 | 4.3 | 8.5 | 3.0 | 8.2 | 0.2 | 10.2 | 2.1 | 97.1 | 29.5 | 0.3 | 0.2 |
| 2016 | 7.8 | 3.1 | 9.3 | 1.8 | 8.1 | 1.3 | 9.3 | 1.3 | 54.0 | 9.2 | 0.5 | 0.2 |
| 2017 | 4.8 | 3.3 | 8.4 | 1.9 | 8.1 | 0.7 | 12.8 | 1.4 | 101.8 | 38.2 | 0.3 | 0.2 |
| 2018 | 6.4 | 3.5 | 9.2 | 1.9 | 7.9 | 0.3 | 10.4 | 0.6 | 88.8 | 29.0 | 0.3 | 0.1 |
| 2019 | 5.2 | 3.8 | 8.2 | 2.3 | 7.6 | 0.1 | 11.5 | 1.0 | 103.9 | 26.6 | 0.2 | 0.1 |
| 2022 | 6.9 | 4.9 | 8.4 | 2.5 | 7.8 | 0.2 | 10.1 |
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126.9 | 83.3 | 0.2 | 0.6 |
| 2023 | 8.3 | 5.4 | 9.6 | 2.4 | 7.8 | 0.2 | 10.7 | 0.7 | 66.4 | 66.1 | 0.2 | 0.1 |
| 2024 |
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Figure 2. Spring and Fall Condition Plot
Figure 2. Average daily measures of air and water temperature, pH, dissolved oxygen (DO), total dissolved solids (TDS) and water level (stage) per monitoring year in spring and fall.
2.3. Annual Captures
## `summarise()` has grouped output by 'Period'. You can override using the
## `.groups` argument.Since 2008, a total of 5,046 juvenile CCT and 8,216 juvenile Coho Salmon have been captured during spring trapping. Annual captures of CCT have ranged from 45 to 849 (mean = 360) while CO captures have varied from 335 to 913 with an overall mean of 587 fish (Figure 3 and Figure 4, Table 5 and Table 6).
As expected, most fish are captured in the Spring. Catches of CCT have ranged from 45 to 849 during spring (mean = 360 \(\pm\) 276.5) compared to only 1 to 9 fish during fall (mean = 2 \(\pm\) 2.8).
Annual Captures Figures and Tables
Figure 3. Spring - Total annual catches
Figure 3. Total annual catch of CCT and Coho Salmon during Spring fence monitoring.
Table 5. Spring - Total annual catches
| Year | Start | End | # Days Sampled | Med. | Min | Max | n | Mean | SD | Min | Max | Med. | Min | Max | n | Mean | SD | Min | Max |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2008 | Apr-21 | May-31 | 41 | May-20 | Apr-21 | May-31 | 756 | 139.1 | 27.6 | 90 | 280 | May-17 | Apr-25 | May-31 | 512 | 118.1 | 10.7 | 84.0 | 150 |
| 2009 | Apr-19 | Jun-07 | 50 | May-16 | Apr-20 | Jun-03 | 225 | 163.3 | 22.9 | 115 | 265 | May-20 | Apr-24 | Jun-07 | 658 | 100.2 | 11.0 | 11.0 | 160 |
| 2010 | Apr-19 | May-30 | 42 | May-13 | Apr-19 | May-29 | 502 | 149.7 | 26.1 | 110 | 285 | May-13 | Apr-20 | May-30 | 477 | 118.0 | 15.7 | 80.0 | 183 |
| 2011 | Apr-19 | Jun-06 | 49 | May-15 | Apr-23 | Jun-05 | 624 | 155.3 | 32.5 | 95 | 400 | May-17 | Apr-20 | Jun-06 | 602 | 113.1 | 12.8 | 80.0 | 147 |
| 2012 | Apr-16 | Jun-04 | 50 | May-08 | Apr-23 | Jun-01 | 465 | 160.1 | 33.7 | 80 | 335 | May-13 | Apr-16 | Jun-04 | 689 | 107.8 | 12.4 | 75.0 | 145 |
| 2013 | Apr-14 | Jun-01 | 49 | May-09 | Apr-16 | May-30 | 461 | 161.4 | 26.5 | 95 | 350 | May-12 | Apr-15 | Jun-01 | 913 | 106.7 | 9.9 | 83.0 | 150 |
| 2014 | Apr-24 | Jun-07 | 45 | May-09 | Apr-27 | Jun-02 | 76 | 142.1 | 29.2 | 70 | 310 | May-12 | Apr-26 | Jun-05 | 376 | 103.2 | 12.4 | 80.0 | 223 |
| 2015 | Apr-10 | May-31 | 52 | May-09 | Apr-15 | May-28 | 141 | 158.1 | 37.4 | 85 | 260 | May-13 | Apr-11 | May-31 | 761 | 109.3 | 11.7 | 78.0 | 152 |
| 2016 | Apr-03 | Jun-04 | 63 | Apr-26 | Apr-05 | May-15 | 77 | 147.5 | 37.4 | 88 | 250 | May-05 | Apr-05 | Jun-04 | 817 | 108.0 | 13.4 | 0.0 | 162 |
| 2017 | Apr-05 | Jun-11 | 68 | May-24 | Apr-20 | Jun-09 | 65 | 185.1 | 64.0 | 120 | 470 | May-20 | Apr-05 | Jun-11 | 335 | 113.4 | 12.8 | 80.0 | 162 |
| 2018 | Apr-21 | Jun-11 | 52 | May-04 | Apr-26 | May-27 | 45 | 167.4 | 28.2 | 120 | 230 | May-19 | Apr-21 | Jun-11 | 647 | 101.4 | 11.1 | 9.0 | 170 |
| 2019 | Apr-18 | Jun-07 | 51 | May-06 | Apr-18 | May-30 | 571 | 146.1 | 27.6 | 95 | 260 | May-13 | Apr-24 | Jun-05 | 405 | 115.4 | 12.9 | 10.7 | 152 |
| 2022 | Apr-28 | Jun-13 | 47 | May-19 | Apr-29 | Jun-13 | 189 | 168.5 | 33.6 | 98 | 430 | May-21 | Apr-28 | Jun-10 | 366 | 113.7 | 13.0 | 80.0 | 170 |
| 2024 | Apr-12 | Jun-05 | 55 | Apr-29 | Apr-17 | Jun-03 | 849 | 159.8 | 37.1 | 50 | 360 | May-10 | Apr-18 | Jun-04 | 658 | 97.5 | 17.6 | 48.0 | 174 |
Figure 4. Fall - Total annual catches
Figure 4. Total annual catch of CCT and Coho Salmon during fall fence monitoring.
Table 6. Fall - Total annual catches
| Year | Start | End | # Days Sampled | Med. | Min | Max | n | Mean | SD | Min | Max | Med. | Min | Max | n | Mean | SD | Min | Max |
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| 2008 | Oct-14 | Nov-22 | 40 | Nov-03 | Nov-03 | Nov-03 | 1 | 440.0 |
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440 | 440 | Nov-02 | Oct-31 | Nov-03 | 5 | 638.0 | 78.9 | 540 | 720 |
| 2009 | Oct-14 | Nov-22 | 40 |
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Nov-03 | Oct-17 | Nov-18 | 12 | 648.3 | 84.1 | 490 | 790 |
| 2010 | Oct-23 | Nov-26 | 35 | Nov-11 | Nov-11 | Nov-11 | 1 | 290.0 |
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290 | 290 | Oct-25 | Oct-24 | Nov-22 | 37 | 640.1 | 91.5 | 405 | 780 |
| 2011 | Oct-18 | Dec-02 | 46 |
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Nov-12 | Oct-26 | Nov-23 | 30 | 650.5 | 82.9 | 370 | 795 |
| 2012 | Oct-14 | Dec-02 | 50 | Oct-28 | Oct-28 | Oct-28 | 1 | 580.0 |
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580 | 580 | Nov-01 | Oct-14 | Nov-20 | 17 | 583.2 | 107.1 | 300 | 690 |
| 2013 | Sep-29 | Dec-01 | 62 |
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Nov-06 | Nov-02 | Nov-18 | 83 | 631.7 | 59.7 | 490 | 790 |
| 2014 | Oct-04 | Nov-30 | 58 | Oct-28 | Oct-28 | Oct-28 | 1 | 430.0 |
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430 | 430 | Oct-28 | Oct-15 | Nov-27 | 91 | 627.8 | 87.8 | 330 | 830 |
| 2015 | Oct-08 | Dec-08 | 62 |
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Nov-08 | Oct-12 | Dec-02 | 77 | 600.0 | 89.4 | 350 | 750 |
| 2016 | Oct-07 | Dec-05 | 60 |
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Nov-01 | Oct-24 | Nov-17 | 9 | 632.8 | 77.9 | 510 | 750 |
| 2017 | Oct-11 | Dec-05 | 56 | Nov-19 | Nov-19 | Nov-19 | 1 | 470.0 |
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470 | 470 | Nov-15 | Oct-18 | Dec-04 | 19 | 592.4 | 133.3 | 330 | 770 |
| 2018 | Oct-08 | Dec-04 | 58 | Nov-01 | Nov-01 | Nov-01 | 1 | 330.0 |
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330 | 330 | Nov-14 | Oct-26 | Nov-28 | 25 | 605.5 | 91.0 | 380 | 790 |
| 2019 | Oct-08 | Dec-10 | 64 | Oct-16 | Oct-16 | Oct-16 | 1 | 390.0 |
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390 | 390 | Oct-25 | Oct-16 | Nov-17 | 22 | 566.8 | 110.2 | 340 | 710 |
| 2022 | Oct-11 | Nov-16 | 37 |
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Nov-03 | Oct-24 | Nov-06 | 125 | 612.7 | 97.5 | 220 | 750 |
| 2023 | Sep-26 | Nov-17 | 45 | Nov-02 | Nov-02 | Nov-16 | 9 | 239.1 | 108.9 | 152 | 430 | Oct-18 | Oct-11 | Nov-16 | 272 | 571.3 | 96.5 | 220 | 740 |
2.4. Migration Timing
2.4.1 Spring Outmigration
Outmigrating juvenile CCT and Coho Salmon were first encountered at the trap over a similar period, from April 05 to April 29 (mean \(\pm\) SD = April 19 \(\pm\) 6 days) for CCT and April 05 to April 28 for Coho (mean \(\pm\) SD = April 18 \(\pm\) 7.3 days). On average 50% of all CCT had passed the fence by May 11\(\pm\) 11.7 days while half of Coho Salmon migrants had passed the fence by May 15\(\pm\) 6.6 days. Despite similarities in when migrations started and the timing that most migrants had past the fence, there was a noticeable difference in the timing of peak migrations (the date when the greatest number of fish passed the fence). For Coastal CCT, the overall mean \(\pm\) SD peak migration occurred on May 07(\(\pm\) 8.2 days) (Figure 5) whereas overall mean peak Coho Salmon migration occurred more than a week later on May 15 (\(\pm\) 7.1 days) (Figure 6). Total number of daily captures of CCT and Coho Salmon per year are presented in Figure 6 and Figure 7, respectively.
2.4.2 Fall Return Timing
Adult Coho Salmon have been detected at the fence as early as October 11 and as late as November 02, though most of the run (50%) arrive within a week of November 05 (Figure 14 to 19). Relative to spring sampling, CCT are encountered less frequently in the fall and arrival timing appears to be considerably more variable (Figure 20 to 22).
Spring and Fall Migration Timing Tables and Figures
Figure 5. Spring - Overall Capture Timing
Figure 5. Overall median spring capture timing.
Figure 5. Spring - Median CO Capture Timing Across Years
Figure 6. Median spring cpature timing
Figure 6. Spring - Median CT Capture Timing Across Years
Figure 7. Median spring cpature timing
Figure 7. Spring - Frequency of Peak CCT Migration
Figure 8. Frequency of peak CCT capture dates during Spring fence monitoring.
Figure 8. Spring - Daily captures of CCT per year
Figure 9. Total daily capture of CCT and proportion of total annual captures.
Figure 10. Spring - Total daily captures of CCT across years
Figure 10. Total daily capture of CCT across years.
Figure 11. Spring - Frequency of Peak Coho Migration
Figure 11. Frequency of peak Coho capture dates during Spring fence monitoring.
Figure 12. Spring - Total daily captures of Coho Salmon per year
Figure 12. Number of Coho Salmon captured during each day of spring fence operation since 2008.
Figure 13. Spring - Total daily captures of Coho across years
Figure 13. Total daily capture of CCT across years.
Figure 14. Fall - Overall Capture Timing
Figure 14. Overall median fall capture timing.
Figure 15. Fall - Median Fall CO Capture Timing Across Years
Figure 15. Median fall cpature timing
Figure 16. Fall - Median Fall CT Capture Timing Across Years
Figure 16. Median fall cpature timing
Figure 17. Fall - Frequency of Peak Coho Migration
Figure 17. Frequency of peak Coho capture dates during Fall fence monitoring.
Figure 18. Fall - Total daily captures of Coho Salmon per year
Figure 18. Number of Coho Salmon captured during each day of fall fence operation since 2008.
Figure 19. Fall - Total daily captures of Coho across years
Figure 19. Total daily capture of CCT across years.
Figure 20. Fall - Daily captures of CCT per year
Figure 20. Total daily capture of CCT and proportion of total annual captures.
Figure 21. Fall - Total daily captures of CCT across years
Figure 21. Total daily capture of CCT across years.
2.5 Length Frequency
The length frequency figures shown below shed light on the population structure and behaviours of Coho Salmon and CCT in Simms Creek. The lengths of CCT (50 mm to 223 mm) and Coho Salmon (48 mm to 223 mm) measured at the fence suggest multiple age classes of juveniles are moving out of the system each spring. Assuming that CO <100 mm are Age 0 and CO >100 mm are Age 1 would suggest that 55.20% of all overall migrants are Age 0 and the remainder are Age 1. A wider range of age classes is likely present among CCT, including Age 0 fish (~<80 mm) up to mature fish > 230 mm and upwards of 3+ years.
Mature CCT >230 mm represent <1.90% of the total catch of CCT. However, all mature CCT >230 mm were moving downstream, suggesting that they either 1) moved upstream and spawned prior to the start of fence operation or 2) had overwintered in Simms Creek and were follow fry out in the spring - whether this was their first movement to the ocean is unknown.
Length Frequency Table and Figures
Figure 13. Length Frequency of all CCT
Figure 13. Length Frequency of all CCT.
Figure 14. Length frequency of Coastal CCT across years.
Figure 14. Length Frequency of CCT across years.
Figure 15. Length frequency of all Coho Salmon.
Figure 15. Length Frequency of All Coho Salmon.
Figure 16. Length frequency of Coho Salmon across years.
Figure 16. Length Frequency of Coho Salmon across years.
2.6 What are these fish doing???
CCT show incredible diversity in the timing of their life history behaviours. Throughout their range, spawning has been documented in nearly every month of the year. In Puget Sound for instance, spawning has been reported from November through March and timing is highly variable between years (Losee et al. 2016). The spawn timing of CCT in Simms Creek is unknown, or at least undocumented, however, I would assume it occurs during a similar period to Puget Sound and is equally variable.
The current dataset does provide some insight on spawn timing. Presumably, spawners will be >150 mm in length.
FINISH WRITING THIS SECTION
3. Survival
3.1 What may be driving juvenile abundance
{ 9. Survival, echo = FALSE, warning = FALSE, message = FALSE, include = FALSE} source("SourceFiles/9. Survival.R")
To estimate the number of Coho Salmon that survive from egg to fry, we need to make a number of assumptions:
- All adult Coho Salmon that enter Simms Creek and all juvenile Coho Salmon that outmigrate from Simms Creek are enumerated.
- All adult Coho Salmon that pass the fence will successfully spawn.
- The sex ratio of adults is equal (50% are female, excluding jacks which are assumed male).
- Each female will deposit ~2,600 eggs.Importantly, we also need to consider the proportion of juveniles from each age-class the emigrate each year (and assume juvenile age assignments are accurate). Fish that outmigrate as Age-0 fry will be progeny of fish that spawned the previous fall, while fish that emigrate at Age-1 would have spent a full year in the stream (i.e., spawned 2 falls previous) and Age-1+ fish would have spawned 3 years previous. Using this information, we can then calculate the total number of juveniles produced by each spawning event to calculate egg-to-fry survival.
3.2 What about marine survival (from smolt to spawn)
Additional assumptions are required to estimate the number of juveniles that survive to return as adults:
- Adults spend ~18-20 months at sea (1 winter), regardless of whether they leave Simms Creek as Age-0 or Age-1.
- Jacks return to Simms Creek after ~6-8 months at sea (0 winters).
- All Coho Salmon that are enumerate at the fence originated from Simms Creek (i.e., there are no hatchery fish or strays from neighbouring streams).##————————–